Magnetic circuit structure for high-resolution nuclear resonance spectrometers

ABSTRACT

A pair of shells of approximately half-spherical form have magnetic members mounted therein with the end faces of the pole pieces coplanar with the annular end faces of the shells, coplanarity being achieved by lapping. Distance pieces are placed in notches in the annular end faces of the shells, which are filled with insulating material up to a level below the end faces of the pole pieces.

United States Patent [15] 3,662,304 Bringe et a]. 1 May 9, 1972 [54] MAGNETIC CIRCUIT STRUCTURE FOR [56] References Cited HIGH-RESOLUTION NUCLEAR UNITED STATES PATENTS RESONANCE SPECTROMETERS 7 [72] Inventors: Wolfgang Bringe, Palmbach; Eberhard Querfurth; l-lans-Albr. Schanbacher, both Kaflsmhe; f 'i Semen", FOREIGN PATENTs OR APPLlCATlONS Worth; Wolfgang VIeser, EttlIngen, all of Germany 1.236.672 3/1967 Germany .335/28l [73] Assignee: Siemens Aktiengesellschaft, Berlin and Primary E \eumiwr ceorge Harris Munich. Germany AHOrne \-Edwm E. GreIgg [22] Filed: July 2, 1970 21 Appl. No.: 51,979 [57] ABSTRACT A pair of shells of approximately half-spherical form have magnetic members mounted therein with the end faces of the [30] Foreign Apphcauon Pnomy Data pole pieces coplanar with the annular end faces of the shells, July 25, 1969 Germany ..P 19 37 794.7 o l narity being achieved by lapping. Distance pieces are placed in notches in the annular end faces of the shells, which U.S. are with insulating material up (9 a level below the end [5 l l [III- CI- faces ofthe pole pieces [58] Field of Search ..335/296, 297, 298, 281

7 Claims, 1 Drawing Figure MAGNETIC CIRCUIT STRUCTURE F OR HIGH- RESOLUTION NUCLEAR RESONANCE SPECTROMETERS BACKGROUND OF THE INVENTION The invention relates to a magnetic circuit structure for high-resolution nuclear resonance spectrometers of the type comprising a pair of opposed pole pieces mounted on active magnetic members and having their end faces parallel to each other.

ln yoke structures which are to be used with nuclear resonance spectrometers it is of importance that the end faces of the opposed pole pieces which delimit the active air gap deviate by less than i micron from the ideal plane-parallel shape. This requirement implies that the evenness of the surfaces and the surface roughness must correspond to a still higher order of accuracy.

SUMMARY OF THE lNVENTlON The magnetic structure according to the invention is characterized by a pair of shell members forming a hollow body of rotational symmetry, in the interior of which the active magnetic members are mounted coaxial with the pole pieces, the annular surfaces of the shell members being disposed in the plane of the end faces of the pole pieces. Distance pieces are provided between the annular surfaces of the shell members to define the distance between the same.

This construction of the magnetic structure is characterized by the essential feature of a division into a pair of similar halves, the end faces of the pole pieces and the annular faces ofthe shell members being in one and the same plane. The dimension of the air gap can be controlled by means of the distance pieces which form part of the magnetic structure and are made of a material having a high saturation value of magnetic induction.

The invention also relates to a method of manufacturing the structure, which is characterized in that the annular face of each shell member and the end face of the corresponding pole piece are brought into coplanar relation by means of a machining operation such as lapping and the distance pieces being treated in a simultaneous machining process, suchas lapping to bring the surfaces thereof into coplanar relation.

THE DRAWING An embodiment ofthe invention will be described with reference tothe drawing, which shows a section through the magnetic structure.

THE EMBODlMENT The magnetic structure M comprises a pair of shell members SI and S2 which form together a hollow body of rotational symmetry with somewhat flattenedendportions. ln the interior of the shell members S1 and S2, active magnetic members T1 and T2 are disposed coaxially with each other and integral with the walls of the shells S1 and S2. For instance, members T1. and T2 may be. inserted in circular recesses A1 and A2, a mass of insulating material 7 filling the space between active members T1 and T2 and the shells Sl and'S2 up to a certain level which permits the pole pieces P1 and P2, which are disposed on the active members T1 and T2, to project from the insulating material 7. It is also possible to fasten the active members T l and T2'to the shell members S1 and 82 by means of bolts B or by othermechanical means. The active members T1 and T2 may be permanent magnets or electromagnets having their energizing windings placed on the mantle surfaces thereof in well-known manner.

The pole pieces P1 and P2 are secured to the active mem-' bers T1 and T2'with the aid ofcentering rings Z1 and 22. The shells S1 and S2 in the finished structure form a protective shield .for the magnetic field between'the end faces F land F2 of the'pole pieces P1 and P2 so as. to suppress the influence of external disturbing fields. The spacing a between the terminal faces F l and F2 should have a constant value over the entire end faces F1 and F2, this value being controlled by meansof distance pieces D, which are disposed along the annular faces R1 and R2 of the shell members S1 and S2. The dimension of the distance pieces D controls the spacing a of the end faces F1 and F2. The distance pieces D are of a material of high permeability and form a yoke portion of the magnetic structure M. They are uniformly distributed along the circumference of the annular faces R1 and R2, so as to form a practically uninterrupted ring.

The shell members S1 and S2 are provided with external flanges W1 and W2 which have borings provided therein at uniformly spaced points. Inserted in the borings are bolts SB, which may cooperate with nuts (not shown) to hold the shell members S1 and S2 in firm contact with the distance pieces D. For centering the shell members S1 and S2 relative to each other, annular notches RNl and RN2 are provided in the annularsurfaces R1 and R2 thereof. Inserted in notches RN] and RN2 are centering members Z, which are uniformly spaced and ensure the accurate alignment of the end faces F l and P2 of the pole pieces P1 and P2 opposite to each other.

The production of the magnetic structure M according to the invention comprises the treating of the annular face R1 or R2 together with the corresponding end face F1 or F2, respectively, in a common machining process, such as lapping, to achieve the highest possible degree of coplanarity thereof. This also assures the highest possible degree of evenness of faces F1 and F2. lrregularities due to the machining process, such as edge deficiencies at the end faces F1 and F2 of the pole pieces P1 and P2, which could give rise to distortions of the magnetic field, are possible, according to this method only with regard to the external annular portions of the faces R1 and R2.

By means of a treatment of the distance pieces D in a common machining process such as parallel lapping andthrough subsequent selection, it is possible to achieve with a high degree of accuracy an equal height of the distance pieces. Possibly remaining irregularities in the level of the distance pieces D have only a reduced influence, according to this method, on the parallelity of the boundary surfaces of the active air gap defining the distance a between the end faces F1 and F2. Since the'distance pieces D are disposed on-the annu lar faces R1 and R2 of the shells S1 and S2, deviations in the dimensions thereof become effective ina reduced proportion corresponding to the ratio of the diameter of the end faces F1 and F2 to that of the shell members S1 and S2.

That which is claimed is:

l. A magnetic circuit structure for high resolution nuclearresonance spectrometers comprising a pair of oppositely disposed pole pieces permanently mounted on active mag netic members and having their end faces parallel to each other, characterized in that the magnetic structure (M) comprises a pair of shell members (S1 and S2) forming a hollow body of rotational symmetry, said active magnetic members (T1 and T2) with said pole pieces (Pland P2) being disposed coaxial to each other therein and the annular faces (R1 and R2). of the shell members (S1 and S2) being disposed in the plane of the end faces (F1, F2), of the pole pieces (P1, P2), distance pieces (D) being provided between said annular faces (R1, R2) so as to define the distance a therebetween.

2. A magnetic circuit structure as claimed in claim 1, in which centering members (Z) are disposed along said annular surfaces (R1, R2) in oppositely disposed annular notches (RN1, RN2) therein.

3. A magnetic circuit structure as claimed in claim 1, in which said shell members (S1, S2) are of soft iron.

4. A magnetic circuit structure as claimed in claim 1, in which the active magnetic members (T1, T2)'are embedded up to a level below the end faces (F1, F2) of the pole pieces (P1, P2) in an insulating material (7).

5. A magnetic circuit structure as claimed'in claim 1, in which the active magnetic members (T1, T2) are bolted-to said shell members (S1, S2).

6. A magnetic circuit structure as claimed in claim 1, inwhich said pole pieces (P1, P2) are fastened on said active magnetic members (T1, T2) by means of centering rings (Z1, Z2) threaded thereon.

7. A magnetic circuit structure as claimed in claim 1, in 5 which said distance pieces (D) are of a material having a high saturation value of magnetic induction. 

1. A magnetic circuit structure for high resolution nuclearresonance spectrometers comprising a pair of oppositely disposed pole pieces permanently mounted on active magnetic members and having their end faces parallel to each other, characterized in that the magnetic structure (M) comprises a pair of shell members (S1 and S2) forming a hollow body of rotational symmetry, said active magnetic members (T1 and T2) with said pole piecEs (P1 and P2) being disposed coaxial to each other therein and the annular faces (R1 and R2) of the shell members (S1 and S2) being disposed in the plane of the end faces (F1, F2) of the pole pieces (P1, P2), distance pieces (D) being provided between said annular faces (R1, R2) so as to define the distance a therebetween.
 2. A magnetic circuit structure as claimed in claim 1, in which centering members (Z) are disposed along said annular surfaces (R1, R2) in oppositely disposed annular notches (RN1, RN2) therein.
 3. A magnetic circuit structure as claimed in claim 1, in which said shell members (S1, S2) are of soft iron.
 4. A magnetic circuit structure as claimed in claim 1, in which the active magnetic members (T1, T2) are embedded up to a level below the end faces (F1, F2) of the pole pieces (P1, P2) in an insulating material (7).
 5. A magnetic circuit structure as claimed in claim 1, in which the active magnetic members (T1, T2) are bolted to said shell members (S1, S2).
 6. A magnetic circuit structure as claimed in claim 1, in which said pole pieces (P1, P2) are fastened on said active magnetic members (T1, T2) by means of centering rings (Z1, Z2) threaded thereon.
 7. A magnetic circuit structure as claimed in claim 1, in which said distance pieces (D) are of a material having a high saturation value of magnetic induction. 